Frequency of Birth Control Services with Prescriptions for Unsafe Drugs During Pregnancy

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The summary below is from the full report titled "Documentation of Contraception and Pregnancy When Prescribing Potentially Teratogenic Medications for Reproductive-Age Women." It is in the 18 September 2007 issue of Annals of Internal Medicine (volume 147, pages 370-376). The authors are E.B. Schwarz, D.A. Postlethwaite, Y.Y. Hung, and M.A. Armstrong.

What is the problem and what is known about it so far?

Some drugs can cause birth defects and other problems if a woman takes them while pregnant. The U.S. Food and Drug Administration classifies drugs according to safety during pregnancy. Drugs in classes A and B are safe, whereas drugs in classes D and X are potentially unsafe. Women who receive prescriptions for class D and X drugs should also receive counseling about birth control if they could become pregnant (that is, if they are sexually active with men, have not yet gone through menopause, and have not had a hysterectomy or had their tubes tied). Appropriate birth control services include counseling to avoid sexual activity until after they have stopped taking the drug, prescription of birth control drugs or devices, or regular use of condoms or other nonmedical forms of birth control.

Why did the researchers do this particular study?

The researchers wanted to find out how often women who filled prescriptions for drugs that can be unsafe during pregnancy also received birth control services.

Who was studied?

The researchers studied all prescriptions for class A, B, D, or X drugs filled in 2001 by women age 15 to 44 years and who belonged to a large managed care plan in California.

How was the study done?

The researchers examined health plan data (not medical charts) to look for drug prescriptions and for codes for birth control counseling, birth control drugs, or sterilization procedures (hysterectomy or having had tubes tied). They compared how often women taking safe drugs (classes A and B) and unsafe drugs (classes D and X) received contraceptive services or had a positive pregnancy test. They also looked for differences depending on the type of potentially unsafe drug prescribed.

What did the researchers find?

Women who filled prescriptions for class D or X drugs were no more likely than women who filled prescriptions for safer, class A or B drugs to have received birth control services. One percent of women taking class D and X drugs had a positive pregnancy test within 3 months of the drug prescription compared with 1.4% of women taking class A or B drugs. The researchers did not look at the outcomes of these pregnancies. Women taking the acne drug isotretinoin received birth control services more frequently than women taking any other types of unsafe drugs, whereas women taking cholesterol drugs (statins) received birth control services less frequently.

What were the limitations of the study?

Because the researchers did not examine the medical charts, they could not determine whether women were sexually active or using condoms or other forms of contraception that would not generate a billing code. For this reason, the study might overestimate the frequency of inadequate birth control. It is unknown whether the findings in this specific managed care plan apply to other health care settings.

What are the implications of the study?

Women who could become pregnant and their doctors must remember the importance of birth control when medications that may be unsafe during pregnancy are used.